Mollusks From the Pepper Shale Member of the Woodbine Formation McLennan County, Texas GEOLOGICAL SURVEY PROFESSIONAL PAPER 243-E Mollusks From the Pepper Shale Member of the Woodbine Formation McLennan County, Texas By LLOYD WILLIAM STEPHENSON SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1952, PAGES 57-68 GEOLOGICAL SURVEY PROFESSIONAL PAPER 243-E Descriptions and illustrations of new species offossils of Cenomanian age UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1953 UNITED STATES DEPARTMENT OF THE INTERIOR Douglas McKay, Secretary GEOLOGICAL SURVEY W. E. Wrather, Director For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 25 cents (paper cover) CONTENTS Page Abstract________________________________________________________________ 57 Historical sketch__-___-_-__--__--_l________________-__-_-__---__--_-______ 57 Type section of the Pepper shale member.____________________________________ 58 Section of Pepper shale at Haunted Hill._______________-____-__-___---_------- 58 Systematic descriptions._______.._______________-_-__-_-_-____---__-_-_-_----_ 59 Pelecypoda_ ________________________________________________________ 59 Gastropoda.______-____-_-_____________--_____-___--__-___--__-______ 64 Cephalopoda-_______-_______________________-___--__---_---_-__-— 65 References......___________________________________________________________ 65 Index.__________________________________________________ 67 ILLUSTRATIONS Plate 13. Molluscan fossils, mainly from the Pepper shale__________ Following index in 231314—53 MOLLUSKS FROM THE PEPPER SHALE MEMBER OF THE WOODBINE FORMATION, McLENNAN COUNTY, TEXAS By LLOYD WILLIAM STEPHENSON ABSTRACT My attention was first called to this unit by Mr. R. L. This paper records an assemblage of molluscan fossils from Cannon, in 1926 (oral communication). He informed the Pepper shale member of the Woodbine formation at a me that he had traced a Woodbine-like clay or shale locality known as Haunted Hill, 3.5 miles northwest of Moody, from Hill County, where it was generally recognized McLennan County, Texas. The assemblage includes the follow­ as belonging to the Woodbine formation, southward ing four species previously described by me from the Woodbine formation: Anomia ponticulanaf, Fulpia pinguis, Cyprimeria through McLennan, Bell, and Williamson Counties, to patella, and "Corbula," hillensis. One species common to the the vicinity of Austin in Travis County. Acting CTL Lewisville member of the Woodbine, previously described as this information I visited localities in Hill, McLennan, Eoioffyra sp., is here given the new specific name, Exogyra aquil- and Bell Counties in 1926, and was able to confirm tH lana. The following six additional new species are described: presence of the Woodbine-like shale unit between tl ^ Breviarca (Sanoarca) spiritalis, Brevlarea (Sanoarca) calciana, Gyclorisma nodana, Sinonia lozoi, Parmicorbula moodiana, and Buda limestone below and the undoubted Eagle Ford Aiwhura umbrana. One new variety, Turritalla shitleri pep- shale and interbedded flaggy limestone above. I did perana, is described. The genus Baculites, not previously not at the time have an opportunity to restudy tl ^ recorded from the Woodbine formation, is represented by a section in Travis County. However, on a visit in 1928 fragment of a small smooth unidentified species. I noted several feet of dark noncalcareous Woodbind- The evidence afforded by this assemblage confirms the con­ like clay forming the base of the section (mainly Eagle clusion that the Pepper shale member is the southward ex­ Ford) which intervenes between the Buda limestone tension of the Woodbine formation, and is probably the exten­ sion of the Lewisville member of that formation. below and the Austin chalk above on Bouldin Creek south of Colorado River at Austin. (Stephenson, HISTORICAL SKETCH 1927, pp. 3, 4.) In the Guide Book of the 1951 Field Trip of the East Texas Geological Society (Cretaceous The stratigraphic unit from which the fossils de­ of Waco, Texas Area, p. 155), the thickness of this clay, scribed in this paper were obtained was named the designated Pepper, is given by Adkins and Lozo as 34 Pepper formation by W. S. Adkins in 1933 (Univ. of feet. Texas Bull., 3232, pp. 239, 270, 417-422). This shale The shale composing this unit is only meagerly fo- unit lies between the top of the Comanche series and siliferous and the few macrofossils heretofore found in the flaggy limestones and dark shales that form the base it are poorly preserved. Adkins listed several genera of the Eagle Ford shale (Gulf series) of Late Cre­ of pelecypods, gastropods and ammonites, preserved as taceous age. It crops out in a narrow belt extending delicate impressions, from the type locality of the unit, from McLennan County, Texas, southward through Bell but he did not consider them diagnostic of exact age and Williamson Counties to Travis County. The unit (1933, p. 419). had been known to earlier geologists, some of whom The late Helen Jeanne Plummer (in Adkins, 1933, considered it a southward extending s^ale f acies of the pp. 419, 420) identified arenaceous Foraminifera from Woodbine formation, and others a basal member of the the lower part of the type section of the Pepper shale, Eagle Ford shale. The thickness of the unit in central belonging to the genera Ammobacuities, Ammodiscus, McLennan County is 75 feet or less, from which area and Reaphax. She says, southward it gradually becomes thinner and finally These species have no relation to those of the Grayson or Del Bio formations, but are similar to species in the Eagle Ford and pinches out by overlap in Travis County south of other Upper Cretaceous faunal groups. I feel no hesitancy in Austin. referring this shale to the Upper Cretaceous series. 57 58 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1952 In 1946 Alfred R. Loeblich, Jr., described eleven new spotty, but at levels fossils occur, as shale ammonites at Alli­ species of arenaceous Foraminifera from the type lo­ gator Creek; in fossiliferous limy seams at Haunted Hill. cality of the Pepper shale on Bird Creek, a small tribu­ TYPE SECTION OF THE PEPPER SHALE MEMBER tary of Leon River, 4 miles east-northeast of Belton, The type section of the Pepper shale member of the Bell County, about 500 feet southeast of the Belton- Woodbine formation is in small northwest-facing bluffs Temple highway (U. S. 81). Loeblich says (pp. 132- of Bird Creek, a small tributary of Leon River, 500 feet 133): southeast of the Belton-Temple highway (U. S. 81), Environment.—The writer believes these sediments were de­ about 4 miles east-northeast of Belton, Bell County. posited in shallow waters of low salinity, because of the The member was named from nearby Pepper Creek. presence of abundant siderite and limonite concretions, the presence of large numbers of reworked calcareous forms, the The following description of the type section is adapted absence of any indigenous calcareous Foraminifera in the type from the description of the measured type section given Pepper, the small size of the arenaceous species, the large amount by Adkins and Lozo (p. 130). of organic matter in some of the samples, and the limited mega- fauna, which consists only of mollusks and worms. Section on Bird Creek, 4 miles east-northeast of Belton, Correlation.—The present fauna consists entirely of new Bell County, Teaeas species, and hence cannot settle the question of the correlation Gulf series: Feet of the Pepper formation, but perhaps can be used for com­ Eagle Ford shale: parison when the microfauna of the Woodbine is better known. Limestone, wavy-bedded, yellowish-brown, massive to platy and thin-bedded, witl a At the time Loeblich's paper was published he knew thin bed of bentonite near the middle; of the presence of this assemblage of arenaceous Forami­ locally with ammonites and other n^ol- nifera only at the type locality of the Pepper shale, but lusks, in part fragmentary—————————— 2 + Shale, black, fissile, slightly calcareous, with he informs me that at a later time he found the same abundant globigerinids and other shells—— 1. 5 assemblage in the few feet of dark noncalcareous shale Unconformity immediately overlying the Buda limestone in the Woodbine formation (Pepper shale member) : Bouldin Creek section south of Austin. Shale, purplish-black, noncaicareous, with sele- In recent years the age and stratigraphic relation­ nite crystals, and with yellow jarosite crys­ tals, films and streaks in weathered psrts ships of the Pepper shale have been more critically of the shale; contains arenaceous f oraminif- studied in the Waco area (including parts of Bell, Mc­ ers and thin nacreous shells and impres­ Lennan and Hill Counties) by Adkins and Frank E. sions of mollusks________—————_—_ 22 5 Lozo, and the results of their field and laboratory studies Shale, gypsiferous, with many euhedral sele- are recorded in a paper published as part of "A Sym­ nite crystals_______———————————— 0.6 Clay, sandy, carbonaceous, gypsiferous, with posium for the 1951 Field Trip Sponsored by the East quartz and phosphate pebbles, fish remains, Texas Geological Society" (1951, pp. 101-161). It was lignitized wood and reworked Del Bio [fie] my privilege to participate in this field trip, which was fossils___________________-____ 0. 45 held May 3 to 5, 1951. The fossils described in the Unconformity Comanche series: present paper (U. S. G. S. Coll. 23634) were collected Grayson marl (formerly Del Rio clay) : by me during the course of the trip at the locality des­ Clay, gray, massive, calcareous, fossiliferou«_ 1. 5 ignated "Haunted Hill" by Adkins and Lozo (pp. 134, Limestone, gray, soft, gritty, clayey————„_ 0. 3 185). Clay or marl, exposed downstream——————— 25 + As a result of their study of the Pepper shale Adkins Total + and Lozo interpreted this unit to be a southward ex­ SECTION OF THE PEPPER SHALE MEMBER AT tending shale facies of the Lewisville member of the HAUNTED HILL Woodbine formation. They summarize their conclu­ sions in the following words (1951, p.